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Andrew Tridgell
2ab4d2c6e6
The bump allocator hands out chunks from one big malloc, so AddressSanitizer
cannot see a write that underflows one chunk into its neighbour -- e.g. a
miscomputed F_SUM() that reaches before a file_struct's extras (the
FLAG_HLINKED-without-H bug). Under ASan, poison a small redzone just below
each returned chunk (allocations grow downward from the top of an extent) so
such an underflow becomes a hard use-after-poison report; unpoison a whole
extent whenever its space is reused (reset/reclaim) so legitimate later
allocations never trip over an old redzone. Compiled out entirely without
-fsanitize=address.
Validated: a deliberate write 12 bytes below F_SUM is caught as a
use-after-poison; the existing suite (hardlinks/inc-recurse, daemon, xattrs,
merge) is clean under ASan, so the redzone introduces no false positives.
Also add a require_asan() test helper (mirrors require_tcp) for tests that are
only meaningful under an ASan build.
(cherry picked from commit 402962b7cdea8afb27c0e6e198fef62172c751e3)
(cherry picked from commit 3fbee7e407)